Medical devices for use externally or internally with humans or animals can serve to introduce bacterial, viral, fungal or other undesirable infections. Certain prior art devices become unworkable after a short period of time, and must be replaced. In the case of urinary catheters, for example, frequent replacement can cause excessive discomfort to the patient and prolonged hospitalization. In the case of intravenous catheters used for critical care patients, infections can themselves prove life threatening. Additionally, there is always a threat of exposure to infectious contamination from surfaces that contact patients, from surgical gloves, and from other medical gear and apparatus.
To prevent such contamination, medical devices can be treated with an antimicrobial agent. Known methods of preparing an infection-resistant medical device have been proposed in U.S. Pat. Nos. 3,566,874, 3,674,901, 3,695,921, 3,705,938, 3,987,797, 4,024,871, 4,318,947, 4,381,380, 4,539,234, and 4,612,337.
In addition, antimicrobial compositions useful as coatings for medical devices or for forming the device itself are disclosed in U.S. Pat. Nos. 3,699,956, 4,054,139, 4,592,920, 4,603,152, and 4,667,143. However, such known methods are somewhat complicated or deficient in the results obtained. The art has great need for medical devices which are able to resist microbial infection when placed in the area of the body to which it is applied and which provide this resistance over the period of time which it remains in place. At the same time, these desirable characteristics must be achieved without sacrifice of other well recognized desirable characteristics. In the case of catheters, for example, it is important that any coating thereon leave a surface which provides a minimum of resistance to insertion of the catheter and which does not release a toxic substance to be adsorbed by the body.
Furthermore, some uses of antimicrobial metal compounds including silver salts in antimicrobial coatings for medical devices are known. Also, chlorhexidine and its salts are known to be powerful antiseptics, but the combination of chlorhexidine with silver nitrate has been shown to have prophylactic properties in burn therapy. In addition, the combination of chlorhexidine and sulfadiazine is known in topical applications to exhibit synergism against strains of Pseudomonas, Proteus, and Staphylococcus, as disclosed in Quesnel et al, Synergism between Chlorhexidine and Sulphadiazine, Journal of Applied Bacteriology, 1978, 45, 397-405.